1. Field of the Invention
The present invention relates to an insoluble tannin preparation process, and a waste treatment process employing the insoluble tannin and an adsorption process using a tannin, which are suitably practiced for treating a waste liquid containing nuclear fuel materials, iron ions, and so on.
2. Prior Art
Usually, nuclear fuels such as uranium or thorium remain in the waste liquid drained during the processing of nuclear fuels. An adsorbent which adsorbs the nuclear materials without being dissolved in the waste liquid has been conventionally utilized to treat waste liquid of this kind. Japanese Patent Applications published with Laid-Open Nos. 63-61998 and 1-155947 describe hydrated gel compounds which may be suitably used as the adsorbents.
The prior art hydrated gel compound is manufactured by reacting an aldehyde or an acid such as sulfuric acid or phosphoric acid with persimmon tannin to gel the tannin.
In the preparation process of the hydrated gel compound, however, the persimmon tannin is the only one that can be used to produce the adsorbent for use in the treatment of the above waste liquid. If natural tannin other than the persimmon tannin is used, the tannin cannot be gelled even though aldehyde or acid is reacted therewith. Consequently, the insoluble hydrated gel compound cannot be obtained by the above preparation process.
Furthermore, the conventional treatment process of waste liquid has been carried out using an insoluble adsorbent which has been manufactured beforehand. Therefore, the conventional waste liquid treatment process has been laborious and high in cost.
Moreover, there has also been known another waste liquid treatment process in which nuclear fuel materials such as uranium or thorium are removed by means of flocculation or coprecipitation of iron hydroxide. With this process, however, the resulting precipitates cannot be disposed of since they are noncombustible.